Some statements may merely provide background information related to the present disclosure and may not constitute prior art.
Polymers have been widely used in oilfield industry for its superior properties. These polymers can be used as either linear or crosslinked. The polymers are built with monomers by covalently bonding in series. Most of the crosslinking are also covalently bonded. These polymer products when used in the formation, if not properly broken, will cause damage and impair production. In other applications, when the polymeric materials need to be removed, it is generally difficult due to the strong bonding. Viscoelastic surfactant (VES) fluid is self-assembled small surfactant molecules into giant worm-like micelles to give polymer like performance in fluid. When broken, there is no need to break the surfactant molecules, rather change the self assemble to alter the worm-like micelle structure to spherical micelles. This will lead to loss of the entanglements between worm-like micelle chains and in sequence loss of viscoelastic properties. The non-covalently bonded structure is beneficial to many oilfield applications. However, in order for the VES fluid to behave like a polymer solution, the concentration of the surfactant needs to be at higher level, at least an order of magnitude higher than that of polymers. Although surfactants can give some good features when it is in the formation, it can also be problematic in some other cases, such as forming emulsions with formation oil, alter the capillary behavior in the formation pores.
A new type of self-assembled structure based on hydrogen bonding is studied and disclosed in this application. The materials discussed in this application are mainly small molecules with molecular weight of a few hundreds. The molecules are full of functionalities that are capable of forming hydrogen bonding between each other. When the material is in melt state or in solution, hydrogen bonding makes the material behave like polymeric material to exhibit viscosity and elasticity. The hydrogen bonding can be destroyed by water dilution or elevated temperature, and they are also reversible, i.e. when cooled down or concentrated, the H-bonding reforms and the material behaves like polymer again.